Trying to fix curved cuts w/o new bar or chain

[pondnstream]

Hi ,

Saw husky 3120
Bar 3/8. 0.058 84DL

Recently I’ve been challenged to correct a bar and chain that wouldn’t cut straight but without buying new chain or bar which would be the easiest and probably the best solution but I wanted to see if I could DIY cure the problem of very bad curved cutting.

I did all the following and it cut much straighter but still wasn’t perfect and still wanted to cut a bit to one side:

1. Filed All cutters same length

2. Filed all rakers same height

3. Filed Bar rails same height and square to side of bar

4. Squeezed and hammered the Bar rails snug against chain so that chain doesn’t move from side to side but still slides in bar.

A friend and I spent several hours trying to get the rails closed to the point of being snug against the chain but not too tight. We tried a roller , then hammering , then a large vise. None of these were the perfect solution to move the side rails in the thousandths of inch to the exact spot. In the end we got close but had some hot spots where it was too tight against the chain.

Couple of questions :

a) Does a straight and flat a bar sometimes become uneven and beyond correction ?

b) Does a chain that’s been run in a bar with uneven rails get worn to the point where it won’t cut straight even on a good bar ?

c) was I mistaken by thinking the curve cutting was caused by bar rails gauge that was too wide and my real problem was the chain’s drive links were worn and causing the chain to lean and not stand up straight on the bar ?

d) What’s the best easiest to use tool for closing the rails ?

Thanks

 

[singinwoodwackr]

Yes, yes, don’t know as I’d need more info
What did you use to true the bar rails with?

 

[pondnstream]

To cl

Yes, yes, don’t know as I’d need more info
What did you use to true the bar rails with

To close the rails , we tried several things:

1st , a jeweler’s roller used to squeeze flat stock and make it thinner , we had to add a thin piece of steel over the rail so it would just squeeze at that point .

2nd, carefully hammering

3rd, large vise wit bar 1/4” between jaws and rotating handle to same point and working across the width of the bar.

 

[singinwoodwackr]

Yes, yes, don’t know as I’d need more info
What did you use to true the bar rails

To cl


To close the rails , we tried several things:

1st , a jeweler’s roller used to squeeze flat stock and make it thinner , we had to add a thin piece of steel over the rail so it would just squeeze at that point .

2nd, carefully hammering

3rd, large vise wit bar 1/4” between jaws and rotating handle to same point and working across the width of the bar.

no, what did you make the rails 90* with?

 

[singinwoodwackr]

The single most common cause of curved cuts is the rails out of true. 1/2 a degree off will do it.

And, did you true the rails before or after pinching? Must do it after.

 

[Marley5]

I've had this happen once in 50 years.
Was using a sharpening jig and sharpened the same side of chain twice and unintentionally avoided opposite side...... not good
Chain tension
Worn bar
Did the dummy thing like I did

 

[singinwoodwackr]

I've had this happen once in 50 years.
Was using a sharpening jig and sharpened the same side of chain twice and unintentionally avoided opposite side...... not good
Chain tension
Worn bar
Did the dummy thing like I did

Yea, that would do it

 

[pondnstream]

To dress the rails and make them equal height and square to the side of bar tried the file technique then a disc sander .

Did not go back and re true the rail heights after the pinching and setting the gauge . Will now do that on the disc sander with 90 degree table .

Tried using a file and machinist’s square but have to keep checking, disc sander with right angle table seems better.

 

[Mad Professor]

To dress the rails and make them equal height and square to the side of bar tried the file technique then a disc sander .

Did not go back and re true the rail heights after the pinching and setting the gauge . Will now do that on the disc sander with 90 degree table .

Tried using a file and machinist’s square but have to keep checking, disc sander with right angle table seems better.

Better than a disc sander is a vertical belt sander set at 90 degrees. I've recovered a few bars people were going to toss as scrap.

 

[singinwoodwackr]

To dress the rails and make them equal height and square to the side of bar tried the file technique then a disc sander .

Did not go back and re true the rail heights after the pinching and setting the gauge . Will now do that on the disc sander with 90 degree table .

Tried using a file and machinist’s square but have to keep checking, disc sander with right angle table seems better.

Make sure the sander table is dead on 90*. I use a quality machinist sq and re-check it often.
I’ve used a delta 1x30” belt sander for decades…60g Zircon belts.
I’ve redone dozens of bars the owners thought they’d squared up.

The problem with using a disc sander for bars is it will want to pull/push…up cut and down cut at the same time. A vertical belt sander is a lot better.